Process of treating zinc ores.



Fig.1.

' A. P. CRAFT.

PROCESS OF TREATING ZINC ORES.

APPLICATION FH ED JUNE 23,1917- Patented Mar. 4,1919

" WITNESS.

4Mm aw ED STATES PATENT OFFICE.

AUGUSTUS P. CRAFT, 0F GALENA, ILLINOIS.

PROCESS OF TREATIlN'G ZINC ORES.

Processes of Treating Zinc Ores, of which.

the following is a specification.

My invention relates to processes of treating roasted zinc ores and its object is to' obtain a yield of higher quality and in which particularly the impurities which are in such fine, pulverulent condition that they can not be effectively and economically separated from the ore according to present processes, may be eliminated.

VVith this object in view my process is embodied in the steps hereinafter described, and an apparatus for carrying out such process is illustrated in the accompanying drawings.

In these drawings, Figure 1 is a longitudinal sectional elevation of a zinc ore magnetic separating mechanism, Fig. 2 aplan view thereof partly in section, Fig. 3, a section on line 3-3 of Fig. 1, and Fig. 4, a detail perspective of the fine mesh screen.

The quality of zinc ore is determined mainly by the percentage of metallic zinc contained therein'and the prices per ton of the zinc are measured by these percentages. In zinc sulfid ores such as are found in the \Visconsin, Galena and Joplin districts, the principal impurities retained in the ore, after roasting and magnetic separation, are lime and iron pyrites. exist mainly in a fine condition in the ore and are carried by and form part of the fine body of dust or powder to which part of the ore is reduced in its various treatments of crushing, concentrating, drying, roasting, shaking and separating. My nvention consists in separating this finer body; of orefrom the mass after the steps of roasting and separation of the larger particles of iron therefrom, for the purpose of carrying with it the lime, fine ir'on pyrites or flour iron and other fine impurities, and then subsequently and separately treating this body according to well known ,methods to separate the impurities therefrom.

The drawings show an apparatus designed to carry out these processes. In these drawings 1, indicates a magnetic separator to which the ore is conducted after it has been concentrated and dried and roasted or Specification of Letters Patent.

These impurities Patented Mar. 4, 1919.

Application filed June 23, 1917. Serial No. 176,483.

oxidized, and 2, indicates an agitating,

gravity-feed, inclined table to which the ore is fed.

which serve to attract and thus separate the larger particles of iron from the ore, suchparticles being attracted to and conveyed away by means of conveying bolts 4:,

around the magnets. A magnetic separator of this kind is well known. This magnetic separator is capable of extracting only the larger particles of iron and of course is ineffective to separate the lime'from this ore.

In ore separating mills'a. plurality of such separators with their tables are employed.

In carrying out my invention, at the lower discharge end of the table 2, I provide screen 5, which is preferably of about mesh-and of such fine degree of mesh as to permit only the small, substantially pulverulent particles of the ore, such asare capable of separation from the'impurities by means of the oil flotation process or the slime table process, and incapable of separation by the dry process, to pass through the same. This screen is agitated, to aid in the sifting of the ore and to this end the screen may be made part of or attached to the shaking table 2, as shown. The fine body of ore that passes through this fine mesh screen will carry with it the lime, iron pyrites and similar fine impurities that are mixed with and carried along by the dust or pulverized body of the mass of ore. The mass of small particles thus collected is then capable of ready treatment by a wet process, sucli as the slime table method which is well l own and which may be successfully used to extract the lime and pyrites and other impurities therefrom, and which process can not be successfully used with the ore in the form of the larger particles.

In the ordinary zinc dressing operation, this fine body of ore is carried along with the coarse articles and the fine impurities will be retained, owing to the fact that they can not be separated by the dry process, and they tend to greatly depreciate the quality of the ore, and to lower its percentage of metallic zinc, and therefore. greatly decrease the price per ton that is paid therefor as compared with ores which are free from such impurities. The process therefore not only eliminates the mass of fine ore from the coarser particles and raises the percentage of the latter mass, but also enables the body of fine material to be effectively dressed so Above this table depend magnets 3,

'than fifty. mesh to the inch to separate and collect the fine ores therefrom and then subjecting such collected body of particles of ore to a wet separation process to remove the lime, iron pyrit'es and other impurities.

In Witness whereof, I have hereunto set my hand and seal at Indianapolis this 10th day of June, A. D. nineteen hundred and seventeen.

AUGUSTUS P. CRAFT.

Witnesses H. P. Doonrrrnn,

M. L \VI-IEELER.

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